Process of mixing metallic salt in asphaltic compounds



Patented July 17, 1928.

res,

FRANCIS L. CARSON, BERKELEY, CALIFORNIA.

PROCESS OF MIXING METALLIC SALT IN ASPHALTIG COMPOUNDS.

No Drawing. Application filed May 13,

It is known at the present time, that the use of metallic salt, such as copper sulphate, aluminum sulphate, iron sulphate, etc., added to fluid asphalt or like bituminous material, produces degrees of hardness, toughness, etc., proportional to the amount of the metallic salt added, when other vital conditions can be maintained. The chemical expression for the result of the reaction occurring upon the bringing together of the asphalt and metallic salt, is lowering of the penetration. When using asphalt of 70 penetration, by the addition of various amounts of copper sulphate or other metallic salt, that penetration can be reduced to 65, 60. 55, etc, according to the relative quantities of asphalt and metallic salt.

Bituminous compounds have a wide range of use, for instance, for pavings, ditch linings, roofing, painting, tank lining, liquid container linings, waterproof surfacing. rope impregnation, etc. The compound must have difi'erent degreescf hardness, toughness, -etc., depending upon the .use to which it is to be put and it is therefore neces sary in the manufacturing process, to be able to determine the exact proportion of metallic salt and bitumen, to be mixed. My invention seeks to provide a method for accomplishing this, whereas it can not be uniformly accomplished under the present day methods.

It is a further object, to provide a compound so rich with mineral salt, that a ,small volume of said compound may be used to process many times that volume of bitnment without the ,violent eflervescing and temporary volume increase which follows initial introduction ofmineral salt into hot bitumen. a

The present practice is to add a desired quantity of metallic salt to either the hot asphalt alone, or to add such salt to the hot asphalt after the latter has been mixedwith hot rock aggregate, such for example s is used in road construction. When the netallic salt is added to the liquid asphalt, there follows a chemical and mechanical reaction which may be described as a boiling or efiervescing, and during this reactionary period, a volume is occupied. many times greater than that originally occupied by the substances before bringing them together. After this reaction has. concluded, the mixture of asphalt and the metallic salt, sub- 1926. Serial No. 108,975.

sides to a volume approximately equal to that originally occupied by the vsubstances, before they Were broughttogether. The actual reaction which occurs upon the bringing together of the metallic salt and asphalt, is as follows:

The point of liquefaction of asphalt is usually higher than the boiling point of water. Copper sulphate contains a large percentage of the water of crystallization which breaks free at a low temperature in the form of steam. Introducing copper sulphate to asphalt with the latter at a temperature higher than 213 F. and the consequent breaking loose of the water of crystallization, causes the entire massv to become impregnated with steam and the increase in volume is the same as that which occurs when water finds its way into hot asphalt.

As stated above, the difl'erent degrees of hardness, toughness, etc., prescribed for different asphaltic compounds, can be obtained only when it is possible to accurately control the amount of metallic salt to be used in a givenvolume of liquid asphalt. It must also be possible to control the amount of heat for a prescribed period of time, but these ends cannot be successfully attained with the present method. In the fii'st place, the salt is added directly to a rather large volume of the asphalt and that produces an increase in volume'so great that it is the most difiicult step .to control in the present manufacturing process. Furthermore, different temperatures ofthe rock aggregate with which it is desired to mix the asphalt, which temperatures can not be accurately controlled under present day methods, and different degrees of porosity of such aggregate, will afiect the character of the final mixture in ways which are indeterminateat the start. In short, the variations of temperatureof the mineral ag regate and the asphalt, and the different adsorbent or porous qualities of the aggregate, are factors and easily controlled amount of liquid asphalt, to obtain a. mixture super-abundantlyrich-with the'metallic salt and capable of standing dilution, the component parts of this mixture being definitely known quanimately forty-five titatively, as 'well as knowing the degree of heat which was applied during-the mixing and reactionary periods, and the length of time involved. After the reactionary period, upon bringing'together of the liquid asphalt and the metallic salt, there will be no further chemical reaction when a volume of this mixture is added to a larger known quantity of liquid asphalt, many times the first named volume. Thus, the final mixture Will contain a predetermined proportion of asphalt and metallic salt, insuring that it will meet requirements, and this result is attained without the usual difficulties which accompany endeavors to process large quantities of asphalt wit-h mineral salt.

The above described rich mixture, when using copper sulphate, should embody 10 percent or more by weight-,of copper sulphate, and at the termination of the period of efl'er'lescense, the volume may be expanded forty times, by the addition of' are set at a minimum of one-eighth of one.

percent copper sulphate and a maximum of three percent copper sulphate.

If desired, instead of forming the rich mixture as above defined, the following steps ma be employed;

.opper sulphate or other mineral salt may be disolved 'in hot water, and hot asphalt and clay mixed with this solution to form an emulsion, and such a percentage of the mineral salt is used, as to provide this emulsion with a large percentage thereof. Then, later, after the water content of the emulsion has evaporated leaving a net residue of asphalt, mineral salt and clay in the original approximate volume and form of the asphalt treated, a predetermined volume, of tlns processed material may be used. to process many times that volume of hot asphalt. 4 In forming the emulsion in a preferred manner, copper sulphate is added to the water with which the asphalt and clay are to be mixed, the quantity of sulphate being such that it will approximate ten percent or more of the asphalt content of the emulsion. Preferably, this emulsion consists of approxpercent solution of water and copper sul phate,

percent asphalt, forty-five and ten percent clay. With this rich mixture or emulsion, after its water con tent has evaporated, a large quantity of hot asphalt may later be processed to reduce the penetration of the asphalt and raise the melting point of the same, so that the product will be'well fitted for use as a paving material. I l

The -mere mixing together of Water, asphalt and cla is old. The product however is too soil: forv practical use, because in the mixing of asphalt with water, the selected asphalt must havea liquefying point below the temperature at which water will beconverted into steam. Consequently, the product is very soft, pliable, and convertible into liquid at atmospheric temperatures, and is not fit for most industrial uses,

particularly paving. By processing it how u carr in out m invention in so rocessin the material, the desired results are obtained without the trouble, inconvenience, inaccuracies and other difliculties which are now practically unavoidable. The liquid asphalt, containing metallic salt in the proper percentage, prepared as above described, can now be added to the hot aggregate of rock, etc., and this, irrespective of the temperature of, or the absorbent qualities of the aggregate, will produce a resulting compound containing the rcentage of metallic salt desired or speci ed.

From the foregoing, it will be seen that I have provided. a new and. improved process for mixing asphaltic or other bituminous compositions, containing metalhe salt, and that any desired proportion'ofv the salt may be embodied in any quantity of the mixture, so as to impart thereto the desired degree of toughness, hardness, etc.

The first mixing of asphalt and metallic salt, carried out in the practice of my invention, can be. conducted with a relatively small volume and hence, the chemical re-' action and the consequent boiling and expansion, is not so hard to contend with as in the present day method. Moreover, during this mixing operation, the component parts may be sub ected to any prescribed.

or predetermined heat and for any specified or desired length of time. Thus, the chemical reaction can be made to take place with exactness and under prescribed conditions as to heat and time of application, which cannot be practically done under the present practice, for the following reasons:

.Paving plants are almost always located outside of corporate limits, are almost invariably temporary structures, and are in the hands of unscientific workmen, it be; ing thus apparent that no fine measure of heat control can be effected.

In. these plants, copper sulphate, mineral Y sired characteristics.

than a minute.

without a proper measure of heat control,

aggregates and asphalt are mixed in batches, the usual mixing time being less Hence, it is obvious, that uniform reaction cannot occur in each batch. 1

With the violent efliQIVGSOQHSB occuring through the breaking loose of steam generated from the moisture content of the coper sulphate, variable through the fact that the heat oi the asphalt and the heat of the mineral aggregates also is variable, no definite check control can be kept on the reaction. In fact, it is uniform practice to ignore such factors entirely, merely taking chances on the final product having the de- Heretofore it has never been practicable to process asphalt at the producing refinery because of the quantities involved in each shipment, the unit for the paving art being the carload of approximately thirty-five (35) tons,and the inability to provide containprs large enough to hold the expanded volume consequent to the introduction of the metallic salts.

Under the improved method herein described, a concentrated solution of mineral salt and asphalt may be made at the refinery, and that concentrated solution or mixture may be used to make tank carloads of dilute solution or mixture containing a bringing together, this I greg men to form an emulsion,

predetermined quantity of the mineral Salt. As I initially process only a relatively small amount of the asphalt with the copper sulphate or the like, it will be apparent that the fine check control so badly needed in asphalt mixing, at paving plants, shall almost automatically be accomplished at the refinery, before the shipment of'the material to the designation at which it is to be used.

I claim: I

1. In the production of a bituminous compound, the mixing together of a known quantityof hot bitumen with a known quan tity of copper sulphate to cause the usual reaction, and bringing together this mixture or" a predetermined quantity thereof with another known quantity of hot bitumen. 7

2. In the production of a .bituminous compound, the mixing-together of a known quantity ofbitumen and known quantity of copper sulphate under the influence of heat, inixture or a predetermined portion thereof with a known' quantitylof hot get-her this mixture with hot mineral agate. e 3. In a production of a bituminous compound. the mixing together of -water and copper sulphate to form a solution and the mixing of this solution with clay and bituextracting the bitumen, and bringing towater content from saideuuilsion, and the introduction ot.,the residue into additional quantities of hot asphalt.

4. In the production of a bituminous compound the mixing together of water and copper sulphate to form a solution and the mixing of this solution with clay and bitumen to form an emulsion, extracting the water content from said emulsion, introducing the residue into additional quantities of hot asphalt, and bringing together this mixture with hot mineral aggregate.

5. The herein described improvement over the known process which involves the heating of bitumen, the mixture of'a-predetermined quantity of copper sulphate with a predetermined quantity of hot bitumen and a violent eftervescing and temporary volume increase of the mixture; said improvement comprising the steps of mixing the entire predetermined phate, with such a small portion of the predetermined quantity of bitumen, as to permit accurate control of the heating, effervescing and temporar volume increase; and later adding this mixture with its superabundance of copper sulphate to the remainder of said predetermined quantity of the bitumen while the latter is hot-- 6. In the production of a' large quantity of bituminous compound processed w1th copper sulphate; the steps of mixing a relatively small known quantity of hot bitumen with a known quantity of copper sulphate greatly in excess of that required to process sai relatively small quantity of bitumen, and mixing a known volume of the first named mixture with many times that volume of bitumen. j 7. In the production of a large quantity of bituminous compound processed with cop per sulphate; the steps of mixing a relatively small known quantity of hot bitumen with a known quantity of copper sulphate great-1y in excess of that required to process said relatively small quantity of bitumen, mixin tu e with many times tliatvolume of bitumen, and mixing mineral aggregate with the last named mixture. 1

8. In the production of a relatively large quantity of bituminous compound processed with copper sulphate; the steps of forming a solution by bringing water and a known quantity of copper sulphate together; mixing this solution with a small quantity of bitumen to produce a mixture containing an amount of he copper sulphate greatly in excess of that needed to process said small amount of bitumen, allowing the water to a known volume of the first named mixpredetermined quantity of copper sulphate, the latter existing in a super-abundanceover that needed with said predetermined quantity of bitumen, for industrial purposes; a

5 predetermined quantity of said compound being hence adapted for processing a volume of bitumen many timesits own volume, for. the purpose of varylng the penetration and FRANoIs L. CARSON, 

